In recent years, thermal transfer systems have been developed to obtain prints from pictures that have been generated from a camera or scanning device. According to one way of obtaining such prints, an electronic picture is first subjected to color separation by color filters. The respective color-separated images are then converted into electrical signals. These signals are then transmitted to a thermal printer. To obtain the print, a cyan, magenta or yellow dye-donor element is placed face-to-face with a dye receiver element. The two are then inserted between a thermal printing head and a platen roller. A line-type thermal printing head is used to apply heat from the back of the dye-donor sheet. The thermal printing head has many heating elements and is heated up sequentially in response to one of the cyan, magenta or yellow signals. The process is then repeated for the other colors. A color hard copy is thus obtained which corresponds to the original picture viewed on a screen.
Dye receiver elements used in thermal dye transfer generally include a support (transparent or reflective) bearing on one side thereof a dye image-receiving layer, and optionally additional layers, such as a compliant or cushioning layer between the support and the dye receiving layer. The compliant layer provides insulation to keep heat generated by the thermal head at the surface of the print, and also provides close contact between the donor ribbon and receiving sheet which is essential for uniform print quality.
Various approaches have been suggested for providing such a compliant layer. U.S. Pat. No. 5,244,861 (Campbell et al.) describes a composite film comprising a microvoided core layer and at least one substantially void-free thermoplastic skin layer. Such an approach adds an additional manufacturing step of laminating the composite film to the support, and film uniformity can be variable resulting in high waste factors. U.S. Pat. No. 6,372,689 (Kuga et al.) describes the use of a hollow particle layer between the support and dye receiving layer. Such hollow particles layers are frequently coated from aqueous solutions that necessitate a powerful drying stage in the manufacturing process and may reduce productivity. In addition, the hollow particles may result in increased surface roughness in the finished print that reduces surface gloss. It would be advantageous to provide a compliant layer that enables a high gloss print to be obtained. It would also be advantageous if the technology used to provide such a compliant layer also enables a matte-like print to be obtained if a low gloss finish is desired. It would be further advantageous if this low gloss finish can further be enhanced by the incorporation of additives like matte beads in an aqueous subbing layer.
U.S. Pat. No. 6,897,183 (Arrington et al.) describes a process for making a multilayer film, useful in an image recording element, wherein the multilayer film comprises a support and an outer or surface layer and between the support and the outer layer is an “antistatic subbing layer” comprising a thermoplastic antistatic polymer or composition having preselected antistatic adhesive and viscoelastic properties. Such a multilayer film may be used in making a thermal-dye-transfer receiver element comprising a support and a dye receiving layer wherein between the support and the dye receiving layer is a subbing layer. However, this patent fails to mention the importance of antistatic subbing layer adhesion to the dye receiving layer and to the support (or substrate) during printing and immediately after printing is made. Also, no mention is made of the importance of printing under hot and humid conditions, and lack of humidity sensitivity of the subbing layer compositions. U.S. Patent Application Publication 2004/0167020 (Arrington et al.) has similar disclosure in that it does not make any reference to adhesion of the dye receiver layer to the support during printing, immediately after printing, printing under hot and humid conditions, or humidity sensitivity of subbing layer compositions.
Known polymer composite laminates used on the faceside (imaging side) of dye-thermal receiver elements have a top skin layer of polypropylene (PP) onto which can be extruded a dye receiver layer (DRL) containing a polyester/polycarbonate blend. A known subbing layer used between the composite laminate support and the dye receiving layer (DRL) is antistatic and is a blend of 70 wt. % PELESTAT® 300 (polyethylene-polyether copolymer) and 30 wt. % polypropylene (PP). The rheology of these two components is such that PELESTAT® 300 encapsulates the polypropylene (PP), so that the continuous phase in the subbing layer is PELESTAT® 300. The PELESTAT® 300 acts as an antistatic material as well as an adhesive component to polymer laminate support skin layer and the dye receiving layer (DRL). This antistatic subbing layer, however, is significantly humidity sensitive, has poor adhesion, and does not survive borderless printing (edge to edge) when tested under hot and humid conditions such as 36° C./86% RH. In addition, receiver elements containing this subbing layer show poor scratch performance. Moreover, as stated previously, the application of a composite laminate film requires an additional manufacturing step.
Copending and commonly assigned U.S. Pat. No. 7,993,559 and U.S. Publication No. 2010/0330306 (both filed Jun. 24, 2009 by Dontula et al.) describe imaging elements having multiple extruded layers included extruded compliant and antistatic subbing layers. The image receiving layer can be extruded or coated out of an organic solvent. Two or more of such layers can be co-extruded if desired along with optional extruded skin layers.
In addition, copending and commonly assigned U.S. Pat. No. 7,910,519 (Majumdar et al.) describes image recording elements comprising a support having thereon an aqueous subbing layer and an extruded dye receiving layer.
There remains a need for improved adhesion of image receiving layers (such as dye transfer receiving layers) to the underlying substrate that may include an extruded compliant layer, ensuring no delamination during borderless or edge-to-edge printing. In addition, there remains a need for improved antistatic performance in such imaging elements. Further there remains a need to provide compliant and antistatic subbing layer technology that can be incorporated into the element in an efficient and cost effective manner. It is desirable to improve the scratch sensitivity of image receiving elements.